Roadking II help! Ch. 4 volume drop/muffled sounding

[PeeMonkey]

Was playing the Roadking II today, and out of nowhere the volume drops a bit and starts sounding muffled.. anyone have this happen before? I'm going to try switching out the preamp tube, but the weird thing is the other channels aren't affected. Ch. 3 works just fine when switched to, and when I switch back to Ch. 4 it has a small volume drop and then starts to sound muffled..

 

[PeeMonkey]

Wtf. its like the preamp section is all messed up. If I turn the Treble all the way up, the volume goes off completely, turn it off and the volume comes back but it's still muffled sounding, wtf is wrong with ch. 4.

 

[wildchild666]

its wierd that you mention that cause i just got a dual rectifier roadster last week and in the studio its been dropping by 5 to 10 dB and then going back up again and its just in channel 3!! Let me know if you find out anything!!

 

[PeeMonkey]

It looks like its either a bad pot or a bad relay. Giving mesa a call today.

 

[PeeMonkey]

Awesome!! Mesa Boogie rocks, excellent customer service, glad to be using their products, I called them and they updated the warranty info with my info under it, so I'm still covered under the warranty. I bought this second hand and they didn't need original receipt. Now I need to just take it to a authorized center to have it fixed.

FIXED!

 

[Armando]

So did you ever find out what the issue was??

 

[Armando]

I came across an older post in which suggests that russian preamp tubes(12AX7) may be the culprit here. Was that the case in your situation??

 

[Armando]

You know I had to post here because I had the "exact" same scenario happen to me, down to the issue only occurring on ch. 4. I purchased a set of power tubes(6L6s) and 2-12AX7s( V3 and V4) thinking this would be tube related but replacing these tubes did absolutely nothing. I then started checking all the switches on the rear panel of my RK Series I head and all of a sudden, I see that the Speaker selection switch for Ch. 4 was in the middle position(A&B). The problem with that is that I have 2-Mesa 4x12 Trad. Recto 8 ohm cabs plugged into the two 4ohm outputs for Speaker A selection and have the "dummy plug" plugged into the first 4 ohm output for Speaker B selection. Somehow, the switch must have been bumped from "A" only to "A&B" accidentally. In any case, this solved the volume/level drop issue completely.

Now I'm just wondering if any damage may have occurred from this load mismatch. I know when it first happened( level drop/hum) it caused one of the two 6L6s(to the immediate left of the 2-Rectifier tubes) to glow intensely all of a sudden (when I first heard the level drop when footswitching to Ch. 4 from Ch. 3). Anyone know if this could cause any physical damage to any components?

I would appreciate any info on the subject. Thanks in advance!

 

[pokerrules47]

Both of you should check v3 and v5 to see if they are chinese or russian. Should be silkscreened right onto the 12ax7. If they are russian, call mesa and have them send you some chinese ones.

As far as the power tube redplating, just buy some spare tubes and watch it. A lot of the time, a tube will redplate and then go back to normal. If it happens again, shut it down and replaced both of the tubes in that set.